Using nanoporous carbon membranes in fuel cells Ramanathan Ramnarayanan 1 , Ramakrishnan Rajagopalan 2 , Thomas E. Mallouk 1 and Henry C. Foley 2 1 Department of Chemistry and 2 Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802 ABSTRACT We have synthesized nanoporous carbon membranes that have monodisperse pores of 4-5 Å. These membranes have excellent size and shape selectivity that makes them an ideal candidate for use as separators in fuel cells. The selectivity of these membranes to gases such as N 2 , O 2 and water gas [carbon monoxide and hydrogen] were measured using a permeation testing unit. These membranes were then tested as separators in fuel cells. INTRODUCTION We are interested in coupling reaction and separation in chemical and electrochemical systems. Advantages in doing this include shifting the equilibrium position of the reaction and increased selectivity to a given molecule, a theme broadly classified as process intensification. Carbon with pores in the range of 4-5 Ǻ possess excellent size and shape selective properties, helping them preferentially separate gases based on their size and molecular weight. These forms of carbon are typically derived from polymers like polyfurfuryl alcohol (PFA), polyvinylidene chloride (PVDC) and Polyvinylchloride (PVC). The ease of synthesis of these materials in powder form and thin membranes on supports provides the flexibility to process these materials for different applications including catalysis and gas separation [1-4]. Reforming oxygenated hydrocarbons using air or steam generates H 2 , CO and CO 2 . In polymer electrolyte fuel cells that operate at low temperatures [50 -120 0 C], CO concentrations as low as 100ppm is a significant poison and CO 2 dilutes the anode stream, causing sluggish anode kinetics and power losses [5]. There are many ways of minimizing this effect. We could envision raising the temperature to about 150 0 C and desorb these poisons preferentially [6,7]. Other options include looking at electrocatalyst clusters such as Pt-Ru and Pt-Mo that improve anode kinetics [5], or, selectively oxidize CO to CO 2 in the presence of water [CO + H 2 O  CO 2 + H 2 ] using catalysts based on Cu-ZnO-Al 2 O 3 and Pt-CeO 2 [9], or use catalytic filters [6,7] that may also function as adsorbents for CO. Other options may include designing cells having compartments for regenerating electrolytes [8]. The routes described above are based on thermal and or catalytic solutions to the poison problem. We are interested in using nanoporous carbon as a selective separator for fuel cell poisons. BB5.4.1 Mat. Res. Soc. Symp. Proc. Vol. 801 © 2004 Materials Research Society